Ceramic and masonry tile floor and wall coverings have been used extensively in the construction of buildings for many years. Such materials are employed for their strength, durability, attractive appearance and excellent thermal insulating properties. Despite their many desirable features, ceramic and masonry materials typically exhibit poor sound and acoustic insulating properties.
It is undesirable to utilize materials having poor sound or acoustic insulating properties in buildings, especially in modern multi-story urban buildings having high population densities, such as apartment or office buildings. Nearly all apartment dwellers, hotel guests and office workers have at one time or another been subjected to irritating, bothersome noise from an adjacent room or an upper or lower level. In addition, certain high security meeting rooms may even require that sound not be transmitted beyond the confines of the room.
Moreover, it is desirable to have a high degree of sound insulation in the walls and panels of mobile homes, campers, motor homes and other recreational vehicles. It is also beneficial for mass transit vehicles such as subways, trains and buses to have relatively quiet interiors for passenger comfort. Moreover, it is desirable to provide quiet environments in cabins of airplanes and marine vessels.
Ceiling, floor and wall assemblies are typically subjected to two types of noise--airborne sound, for example speech or music, and impact noise, for instance from footsteps. Many building codes have been amended and ordinances enacted in response to the demand for reduced noise levels in buildings, to specifically require that ceiling, floor and wall constructions exhibit certain minimum sound and acoustic insulating characteristics. Codes are currently in effect in Los Angeles, Sacramento, Seattle, and Minneapolis. Such codes typically require that ceiling, floor and wall constructions achieve a Sound Transmission Class (STC) rating of at least 50 (or 45 if field tested), as determined by ASTM Standards E90, E336 and E413. This rating provides a measure of the amount of airborne sound transmitted between rooms or floors. In addition, such constructions are also typically required to achieve an Impact Insulation Class (IIC) rating of at least 50 (or 45 if field tested) as determined by ASTM E90, E336 and E492. This rating provides a measure of the amount of impact noise transmitted between rooms or floors.
There are currently a variety of sound insulating materials presently available which are advertised as achieving a STC and IIC of at least 50. These insulators typically utilize materials having numerous air-filled cells, such as foams, a honeycomb construction, one or more fibrous layers, or a combination of these constructions. An example of a sound insulating material employing a fibrous layer is ENKASONIC.RTM. available from Akzo Industrial Systems Company of Asheville, N.C. ENKASONIC.RTM. utilizes a composite matt of nylon filaments which is bonded to a nonwoven fabric. An example of a sound insulating material utilizing a foam layer containing numerous air-filled cells is ETHAFOAM.RTM. from Dow Chemical of Midland, Mich. There are also materials available which employ both a fibrous matt and air-filled compartments or cells. KINETICS.RTM. Type SR Floorboard available from Kinetics Noise Control, Inc. of Dublin, Ohio employs a rigid phenolic treated honeycomb core layer which is molded between two layers of high density glass fibers. In addition, PCI-POLYSILENT.RTM. available from ChemRex, Inc. of Minneapolis, Minn., consists of a layer of latex foam bonded to a polyester matting.
However, all currently available sound insulating materials suffer from a variety of drawbacks. The first of such drawbacks is the relatively high thickness of these materials. The thicker the material, the greater the thickness of each ceiling, floor and wall construction utilizing the sound insulating material and therefore greater the reduction in volume of each room. Moreover, the effect of additional thickness creates an additional concern during the design of multi-story high rise buildings. Furthermore, the use of relatively thick and often rigid sound insulating materials during construction is cumbersome and typically increases the amount of labor required in constructing the ceiling, floor and walls. Such relatively thick and often rigid materials necessitate additional cutting and fitting operations that an otherwise thin and flexible material would not require.
Thus, there is a need for a sound insulating material which meets the STC and IIC ratings imposed by many codes and ordinances and yet which is in the form of a relatively thin and flexible layer. The previously noted materials, KINETICS.RTM., ENKASONIC.RTM., ETHAFOAM.RTM. and PCI POLYSILENT.RTM. have thicknesses of 0.625", 0.4", 0.25" and 0.157",respectively. It would be desirable to have a relatively thin and flexible, effective sound insulating material, which achieved both a STC and an IIC of at least 50, or 45 , if field tested, and having a thickness less than about 0.150".
Another drawback with many, if not all presently available sound insulating materials, is that such materials typically utilize volatile softeners or plasticizers, generally in significant amounts. The volatile softeners or plasticizers are generally released from their host material over time into the surrounding environment. This is particularly undesirable in buildings having limited traffic or infrequently used or poor ventilation, in view of the potential health hazards and disagreeable nature of such compounds. Moreover, for those sound insulating materials which utilize softeners or plasticizers to achieve a pliable, vibration absorbing material, the loss of plasticizer will result in a reduction in the sound insulating ability of the material. Thus, there is a need for an effective sound insulating material which does not require a volatile softener or plasticizer in significant amounts, and therefore will maintain its sound insulating properties over an extended period of time.